Method for hardening metals



Patented Mar. 3, 1936- UNITED STATES PATENT OFF-ICE 2,032,694 METHOD FOR HARDEN'ING. METALS Samuel E. Gertler, New York, N. Y., assignor of one-half to Harry I. Stein, New York, N; Y.

No Drawing. Application June 20, 1933, Serial No. 676,682

Claims. (Cl. 148-7l refractory metal so as to form an extremely hard I surface on the finished article.

It is known in the art that certain refractory metals such as-tungsten, molybdenum, titanium, and chromium, have abrasive compounds such as carbides, borides, silicides and nitrides, which have extreme hardness. These compounds when made up into any particular form are of such extreme hardness as to be unworkable so that their usefulness is extremely limited.

An object of the invention is to provide as a new article of manufacture a metallic member having a surface thickness in the nature of a solid solution of the base metal of the article and an abrasive compound of a refractory metal forming a skin on the finished article, which is extremely hard, but not making the finished article brittle. I

Another object of the invention is to provide methods for providing a metallic article with a surface thickness of the character set forth above.

In carrying out the invention, it is contemplated that various metals, of which steel will be cited as an example, shall be so treated that a surface thickness thereof of the desired character can be obtained. The metal to be treated, for example steel, may first be worked into the desired shape and then processed so that the desired alloying of the metal with an abrasive compound of a refractory metal is accomplished to produce a coating of appreciable depth of a hardness'heretofore not attained in the art.

This process can be carried out inthe follow,- ing manner: The article to be treated is first worked into the proper shape. Assuming that the article is made of steel, theprocess contemplates completely surrounding thesteel article by a powder of any of the abrasive compounds of refractory metals setforth hereinbefore, and then raising the temperature of the article and the powder to approximately 2000 F. The article and the surrounding powder is permitted to remain at this temperature for a period of about one to two hours and then permitted to cool.

When the article has cooled, it will be found to possess a skin' hardness equivalentto that of carborundum. This hardness, which is due to the formation of a solid solution of steel and of refractory metal used, such as any one of the rehot metals onto surfaces.

the abrasive compound of the refractory metal used, extends inwardly from-the surface of the article for an appreciable depth.

If it is desired to increase the depth of the solid solution specified, such increased depth can 5 be accomplished by a slight change in the process of manufacture. In this slightly modified form of process, the article (again of steel) is worked into the proper shape and is then plated with the base fractory metals set forth hereinbefore, namely, tungsten, molybdenum, titanium, and chromium. The plating can be accomplished electrolytically or in any other suitable manner. After the article has been plated with this base refractory metal, it is then heated to a temperature of approximately 2000" F. for a period of about one hour and is then surrounded by silicon or carbon or a suitable compoundof either. at a temperature of about 1500 to 2000 degrees F. The article with its surrounding is permitted to remain at this specified temperature for approximately two hours. As result of this treatment, the articlewhen cool will be found to possess-an altered surface in the nature of a. solid solution of the steel 'andof the refractory metal, which due to the the article, which surface has a hardness equivalent to that of carborundum with anadded strength to the surface solution and to the article as a whole.

Various methods of plating the steel article with a base refractory metal can be followed, but in practice it has been found that admirable results can be obtained by making use of the following steps. The shaped article is raised to a temperature (in the case of steel) in excess of 1500 degrees. The base refractory metal is then sprayed on to the heated shaped article by means of any well known type of ,device for spraying The molten baserefractory metal is sprayed upon-and combined with the" heated metal of the shaped article to, form a surface thickness of the metal of the shaped article and of the refractory metal. When the article has been plated in this manner, 50

it may be hardened as set forth by either silicon or .carbon or a compound of either. If desired,

the process involving spraying can be carried a carbon vapor, silicon vapor, or nitrogen gas before the sprayed metal reaches the surface ofthe heated shaped article. This results in the formation of an abrasive compound of the refractory metal which is sprayed directly upon the should temperatures be employed on the shaped article in excess of the melting point of the metal of the shaped article so that the form of the article will not be altered. In the case of metals having such low melting'point that it is inade visable to heat them to such temperatures as would cause the union therewith of the abrasive compound of a refractory metal, it is advisable to' make use of the invention in the form wherein the refractory material or an abrasive compound thereof is sprayed onto the article while the article, is either cold or preheated below its melting point. a

From the foregoing it will be apparent that the present invention provides a new, simple and efllcient process by means of which metal articles in various forms can be so treated as to have a surface hardness considerable in excess of any hardness heretofore attained, since, in fact, the

- hardness which can be procured in the manner set forth resembles closely the hardness of carborundum or of the abrasive compound used. The article so processed has a skin of extreme hardness, but at the same time the article is not rendered unduly brittle. For this reason it is to be understood that the invention is to be limited only by the following claims.

- thereof.

' I-claim:

1. The method of surface hardening metals which comprises embedding the metal to be hardened in an abrasive compound of a refractory metal to form a skin on said metal in the nature 5 of a solid solution of said abrasive compound of a refractory metal and of the metal of the article.

2. The method of treating metal which comprises shaping the metal into the desired'form, l0

heating the shaped metal to a temperature below the melting point thereof, and spraying on thesurface of said metal while heated a molten abrasive. compound of a refractory metal to cause the forming of a surface thickness of the metal of 15 the article and of the abrasive compound of the refractory metal.

3. Themethod of treating metal which comprises shaping the metal. into the desired form and spraying on the surface of said-metal a 0 molten abrasive compound of a refractory metal to cause the forming of a surface thickness of the metal of the article and of the abrasive compound of the refractory metal.

4. The method of hardening a surface thick- 2 ness of a metallic article which comprises contacting the surface of the article directly with an abrasive compound of a refractory metal under such temperature conditions as to cause the .union of the metal of the article and the compound 30 into a solid solutionthereof.

5. The method of hardening a surface thickness of a metallic article which'comprises heating the article to a temperature below the melting point thereof, contacting. the surface I of the 35 article directly with an abrasive compound of a refractory metal under such temperature conditions as to cause the union of the metal of thearticle and the compound into a solid solution 4O SAMUEL E. GERTLER. 

